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Materials characterization (SEM, TEM, XRD, XPS)

Which correctly compares EDS (energy-dispersive spectroscopy) and WDS (wavelength-dispersive spectroscopy) for analyzing characteristic X-rays in SEM and EPMA?

  1. ABecause it needs no analyzing crystal, EDS has better energy resolution and separates overlapping peaks more easily
  2. BWDS has better energy resolution, while EDS can measure many elements simultaneously in a short time
  3. CWDS measures all elements simultaneously with a single detector without moving its crystal, so it is faster than EDS
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Answer: B. WDS has better energy resolution, while EDS can measure many elements simultaneously in a short time

EDS measures X-ray energies directly with a semiconductor detector, so it acquires the peaks of all elements simultaneously in a short time and is easily attached to an SEM. Its energy resolution is only about 130 eV, however, so it has difficulty separating close peaks such as Si Kα and W Mα, or S Kα and Mo Lα. WDS selects wavelengths by Bragg reflection from analyzing crystals, so its resolution is about 10 eV, an order of magnitude better, and it is also superior for detecting trace elements and for quantitative accuracy; but it takes time because the analyzing crystal angle must be scanned for each element. The choices saying that EDS has the better resolution or that WDS is the faster swap the characteristics of the two.

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